In processes utilizing ionic liquids as catalysts, extraction solvents, or adsorbents, the high viscosity of the ionic liquids (IL) often results in mass transfer limitations on the process. For instance, in motor fuel alkylation using heptachloroaluminate ionic liquids, high shear mixing may be necessary to produce sufficient surface area to overcome the mass transfer resistance. This is especially evident for high viscosity ionic liquids such as some phosphonium ionic liquids, which otherwise have particular selectivity advantages over nitrogen-based ionic liquids. The high shear mixing leads to droplets of ionic liquid being dispersed in the hydrocarbon phase. Small droplets are more difficult to separate after reaction than larger droplets.
Similar mass transfer resistance is expected in other ionic liquid processes, such as alkane disproportionation and reverse disproportionation, gas separation using ionic liquids (such as CO2 and H2S separation from CH4), and extractions using ionic liquids, such as denitrogenation of heavy feedstocks.
Therefore, there is a need for methods for decreasing the mass transfer resistance of the ionic liquid while not requiring significant decrease in droplet size.